The restraint adjuster or slide-buckle is a device forming part of a seat belt system whose function is the adjustment of the length of the belt, harness or webbing and the device employs retaining means including a pair of cooperating jaw members mounted in operative relation to guide means including inclined bearing surfaces. The jaw members are movable in a housing means in one direction toward a clamping position in which the jaw members, with the belt therebetween, are wedged between the inclined bearing surfaces to retain the belt in fixed position, and, by movement of the belt in the opposite direction therebetween, the jaw members are separable to allow the belt to freely move between them.
A key feature of this invention is the selection of a critical angle for the sloping surface of the clamping members together with a critical set of locations for the guide rods. Although a comfortable tolerance latitude exists on the choice of angle, the angle must be chosen so as to exceed a critical value, below which the force required to pull the release means becomes excessive. Similarly, for the locations of the guide rods, they need only be placed so their centers lie on a pair of lines parallel to the clamping member angle; however, in this invention they have been so placed that minimum overall height of the housing is achieved, also.